BERU are an original part manufacturer for companies like Mercedes so they should be good.
The factory ones are the same shape as the eBay one now.
What you need to be sure of is the output voltage, there are several types. 4.4V & 7V are the most common.
You need 4.4V type.
This kit is 4.4V & the module part number is GSE114 the same as you posted so an educated guess is it should be right.
http://www.ebay.co.uk/itm/MERCEDES-C.../252689609445?